Mobile App Promoting Sexual Health for Young Black Men who Have Sex with Men (psh4ybmsm) Men who have sex with men, and particularly Black men who have sex with men (BMSM) have been disproportionately affected by HIV/AIDS since the beginning of the epidemic, but in recent years the impact of HIV among young Black men who have sex with men (YBMSM) has escalated rapidly. More new HIV infections occur among YBMSM (aged 13-29) than any other age and racial group of MSM, with an increase of 48% from 2006-2009. Young MSM account for 45% of all new HIV infections among African American MSM84. The few interventions focused solely on YBMSM, target ages 18-29, leaving a dearth of interventions for teen BMSM; further, research has found that sex education for YMSM is not readily available from friends, family, or schools, with many YMSM relying on older partners, the Internet, and pornography for education. This project will address these gaps and fill an important product niche for community-based organizations, health departments, clinics, and schools serving YBMSM by testing the feasibility of creating a sex positive smartphone app based HIV/STI intervention developed for use by YBMSM ages 14-18. The concept for the intervention was guided by formative work in which an in-person version of the activities, Promoting Sexual Health, was developed and pilot tested, confirming the utility of the approach. psh4ybmsm employs a theory based approach to address essential knowledge, perceptions of risk, peer norms, attitudes and skill with two primary goals: (1) To reduce HIV/STI, psh4ybmsm emphasizes not having sex, partner reduction, avoidance of concurrent partners, condoms and HIV/STI tests; and (2) To improve sexual health and relationships, it helps participants to become clearer about what they do/don't want to do sexually, to communicate their choices, and to learn ways to enhance sexual experience while reducing HIV/STI risk. The project offers a number of innovations, including the creation of the first sex-positive multimedia interactive smartphone app-delivered HIV/STI prevention program specifically designed for YBMSM aged 14-18 that addresses risk reduction and sexual response, a group difficult to reach via in-person intervention; ?the inclusion of content designed to enhance sexual experience, an approach called for by the target audience; a review of the pros/cons of PREP and PEP; content tailoring based on user activity and inputs--for example, based on gender identity, reported number of partners and frequency of sexual activity, the user is guided toward content specifically tailored for their needs; and ?context sensitive delivery of booster content, such as monitoring SMS texts, Instagram, and Twitter feeds for keywords (i.e. hookup, HIV test)--if detected the app responds with context-appropriate content in the moment. Phase I will test feasibility by finalizing intervention content, designing the app using formative research, and developing and usability testing two intervention activities and one context sensitive function. Phase II will complete development and conduct a multi-site randomized controlled trial to assess effectiveness.